1. C++/Java/COM Interoperability
Paul Werbicki
Supervisor: Dr. Rob Kremer
Department of Computer Science
University of Calgary

2. Agenda Background Thesis Conclusion Problem Statement
Statement of Work
Why?
How?
Scope of Work
Conclusion

3. Background
C++
Mature language that bridges low-level performance and object-oriented programming in a high-level language.
Widely used in commercial software development.
Java
Relatively young language that provides cross-platform software development using an extensive platform API.
Ideal for the development of research and commercial APIs.

4. Background Component Object Model (COM)
Microsoft/DEC solution to allow software objects created by different developers/vendors to interact with one another.
COM defines a binary interface for sharing reusable software components.
Used extensively in all Microsoft development tools and productivity software.

5. Thesis – Problem Statement
How can software written in one language be used in another language?
Specifically, how can software written in Java be used in other programming languages such as C++, Visual Basic, Perl, or Javascript?
To what level is it possible to integrate Java with other programming languages, and what limitations currently exist?

6. Thesis – Statement of Work
I propose creating a library that will allow Java classes to be created and used in C++ and COM-compatible programming languages.
Using this library I intend to study, in a non-trivial example, what limitations exist in object-oriented language and component-based language interoperability.

7. Thesis – Why? Application are being built with “off-the-shelf” parts.
Choice of programming language limits interoperability.
Maintaining the same software in multiple languages is costly.

8. Thesis – Why? Different programming languages are used for purposes.
C++ widely used for commercial applications due to its robustness and performance.
Visual Basic is popular for internal applications due to its rapid GUI development.
Researchers/Vendors choose Java for APIs due to its cross-platform capabilities.

9. Thesis – Why?
By encapsulating Java inside of another programming language, developers can re-use existing cross-platform code, while taking advantage of the platform specific features of other languages.
Examples:
Visual Basic GUI with Java business objects.
Speedy computations in C++ with a Java cross-platform communications library.

10. Thesis – How?
Create a library that uses the JNI to encapsulates the JVM.
Provide a proxy-generating program for C++.
Integrate the library with COM to allow COM-compatible languages to directly access objects.

11. Thesis – How?

12. Thesis – How? C++ Proxy classes will be generated as C++ header files.
Stub functions will use the library to interface with Java and marshall parameters between C++ and Java.
Proxies will allow class inheritance with certain limitations (no private/public/protected or virtual functions).

13. Thesis – How? Component Object Model
Using COM interfaces, compatible languages will be able to directly access Java objects.
Example code (see Chap. 4 for more info):
Dim objJavaVM As JavaCOM.JVM
Dim objDate As Object
Dim strTest As String
Set objJavaVM = CreateObject(“JavaCOM.JVM”)
Call objJavaVM.Initialize(“”)
Set objDate = objJavaVM.CreateObject(“java.lang.Date”)
MsgBox “Date= “ & objDate.toString()

14. Thesis - Scope of Work One-way integration:
Only C++ or COM-compatible languages calling Java will be supported.
Future work: Java calling C++ objects or objects written in COM-compatible languages.
Development will be specific to the Windows operating system due to COM dependencies.
Future work: Full inheritance of Java from C++ (currently a limitation of the JVM).

15. Conclusion
Interoperability library allow integration of Java into many different types of projects.
Complex C++ programs to simple Javascript scripts can take advantage of existing Java code.
Java-based APIs are more appealing to developers if they are not forced to use Java.